# the contact pattern on a chipped credit card **URL:** \ **Category:** Factual Questions\ **Created:** [March 24, 2015, 3:01pm UTC](https://boards.straightdope.com/t/the-contact-pattern-on-a-chipped-credit-card/715862 "2015-03-24T15:01:55Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [March 24, 2015, 3:01pm UTC](https://boards.straightdope.com/t/the-contact-pattern-on-a-chipped-credit-card/715862/1 "2015-03-24T15:01:55Z")
I recently received my new AmEx credit card, which includes the “chip and pin” security system. Can someone explain why the chip contacts are shaped the way they are? there are several apparently separate contacts, but some of the contact pads have curved borders, some are skinny, the central one appears to be joined to some of the perimeter ones but has some perforations in it, etc. Why so complex? ---
**Author:** ![I.Dunno](https://avatars.discourse-cdn.com/v4/letter/i/9f8e36/32.png) [@I.Dunno](https://boards.straightdope.com/u/I.Dunno)\ **Post date:** [March 24, 2015, 3:32pm UTC](https://boards.straightdope.com/t/the-contact-pattern-on-a-chipped-credit-card/715862/2 "2015-03-24T15:32:29Z")
I’ve never used them as there are no chip readers here but I’ve wondered why the one on my citi card is smaller than the one on my Chase card and has less sections. They remind me of SIM card patterns. Don’t know how THOSE work either. ---
**Author:** ![Habeed](https://avatars.discourse-cdn.com/v4/letter/h/a587f6/32.png) [@Habeed](https://boards.straightdope.com/u/Habeed)\ **Post date:** [March 24, 2015, 6:43pm UTC](https://boards.straightdope.com/t/the-contact-pattern-on-a-chipped-credit-card/715862/3 "2015-03-24T18:43:25Z")
> [@Machine\_Elf](#): > > I recently received my new AmEx credit card, which includes the “chip and pin” security system. > > Can someone explain why the chip contacts are shaped the way they are? there are several apparently separate contacts, but some of the contact pads have curved borders, some are skinny, the central one appears to be joined to some of the perimeter ones but has some perforations in it, etc. > > Why so complex? Post a photo. If I had to guess, it would be that this complex pattern prevents the electrical system on the reader from trying to read the chip when it isn’t correctly aligned with all of the pins on the reader. Most misalignment would mean that some of the pins on the reader side would be shorted to each other, something you can detect. The reader would have certain pins at a low dc voltage and certain pins connected to ground, and as the card is inserted, the reader would hold off on powering up the power pins or trying to initiate communication with the chip until (a) there are no shorts between the pins and (b) some kind of switch in the reader detects that a card is pressing against the bottom of it. How many pins are there? Even with the most complex architecture, there ought to be only about 6 total pins… (2 for power, 2 for TX, 2 for RX) ---
**Author:** ![MrSquishy](https://avatars.discourse-cdn.com/v4/letter/m/b9e5f3/32.png) [@MrSquishy](https://boards.straightdope.com/u/MrSquishy)\ **Post date:** [March 24, 2015, 7:04pm UTC](https://boards.straightdope.com/t/the-contact-pattern-on-a-chipped-credit-card/715862/4 "2015-03-24T19:04:28Z")
> [@Habeed](#): > > Post a photo… Oh, sure, nice try! :mad: ---
**Author:** ![gazpacho](https://avatars.discourse-cdn.com/v4/letter/g/6f9a4e/32.png) [@gazpacho](https://boards.straightdope.com/u/gazpacho)\ **Post date:** [March 24, 2015, 7:14pm UTC](https://boards.straightdope.com/t/the-contact-pattern-on-a-chipped-credit-card/715862/5 "2015-03-24T19:14:11Z")
> [@Habeed](#): > > How many pins are there? Even with the most complex architecture, there ought to be only about 6 total pins… (2 for power, 2 for TX, 2 for RX) There are 6 pins on my credit cards power ground reset clock VPP higher voltage programing pin data (this is bidirectional allowing sending of commands and receiving data) On some cards there are two extra pins for a data + and data - as an extra io port. ---
**Author:** ![gazpacho](https://avatars.discourse-cdn.com/v4/letter/g/6f9a4e/32.png) [@gazpacho](https://boards.straightdope.com/u/gazpacho)\ **Post date:** [March 24, 2015, 7:18pm UTC](https://boards.straightdope.com/t/the-contact-pattern-on-a-chipped-credit-card/715862/6 "2015-03-24T19:18:44Z")
> **[EMV](https://en.wikipedia.org/wiki/EMV)** > > EMV is a payment method based on a technical standard for smart payment cards and for payment terminals and automated teller machines which can accept them. EMV stands for "Europay, Mastercard, and Visa", the three companies that created the standard. > EMV cards are smart cards, also called chip cards, integrated circuit cards, or IC cards, which store their data on integrated circuit chips, in addition to magnetic stripes for backward compatibility. These include cards that must be physically ... The card pictured in that link looks like the contacts for my AMEX and VISA cards. ---
**Author:** ![Digital\_is\_the\_new\_Analog](https://avatars.discourse-cdn.com/v4/letter/d/a88e4f/32.png) [@Digital\_is\_the\_new\_Analog](https://boards.straightdope.com/u/Digital_is_the_new_Analog)\ **Post date:** [March 25, 2015, 12:13am UTC](https://boards.straightdope.com/t/the-contact-pattern-on-a-chipped-credit-card/715862/7 "2015-03-25T00:13:47Z")
It’s a [smart card](http://en.wikipedia.org/wiki/Smart_card). The SIM card in your phone is a special case of this. You might have noticed that as SIM cards got smaller, the actual pads didn’t change…just the empty plastic around them. Make that a little bigger, and you have a credit card. ---
**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\ **Post date:** [March 25, 2015, 2:44am UTC](https://boards.straightdope.com/t/the-contact-pattern-on-a-chipped-credit-card/715862/8 "2015-03-25T02:44:18Z")
The basic descriptions is that it’s an 8-pin contact in two lines of four, with improved electrical isolation by bringing pin 5 into the centre to partly shield the signal lines from each other. Apart from that, the shape is a mixture of aesthetic (it looks good), kinasthetic (it was easier for the designer to draw that way, using the tools available), physical (it shouldn’t peel or wear off of the card, and chemical (you want to balance the shapes and areas so that plating and etching give even coverage). ---
**Author:** ![Isilder](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@Isilder](https://boards.straightdope.com/u/Isilder)\ **Post date:** [March 25, 2015, 3:52am UTC](https://boards.straightdope.com/t/the-contact-pattern-on-a-chipped-credit-card/715862/9 "2015-03-25T03:52:45Z")
> [@Melbourne](#): > > (you want to balance the shapes and areas so that plating and etching give even coverage). And keep it covered, for protection of the softer substrate. Anyway the contacts are prescribed to be at the proper places, and the card maker can make the pads any size they wish,as long as the cards contacts are large enough … The contacts in the machine are not the same size as those you see on the card. They could just put 8 dots on the card, it seems. Have a look at the wear marks on a used card. ---
**Author:** ![Hail\_Ants](https://avatars.discourse-cdn.com/v4/letter/h/dc4da7/32.png) [@Hail\_Ants](https://boards.straightdope.com/u/Hail_Ants)\ **Post date:** [March 26, 2015, 1:45am UTC](https://boards.straightdope.com/t/the-contact-pattern-on-a-chipped-credit-card/715862/10 "2015-03-26T01:45:24Z")
> [@Digital\_is\_the\_new\_Analog](#): > > It’s a [smart card](http://en.wikipedia.org/wiki/Smart_card). The SIM card in your phone is a special case of this. > You might have noticed that as SIM cards got smaller, the actual pads didn’t change…just the empty plastic around them. Make that a little bigger, and you have a credit card. If you read that Wiki link you’ll see that the technology was developed in the late 70s, which is why the contact pad is huge by today’s standards. Although they’ve been appearing on credit cards for the last ten years or so they’re still not used by consumers for much of anything in America. In fact, the only big user of them in the US is as encryption cards for satellite TV receivers (i.e. DirecTV). Back in the day I got into hacking those and still have a bunch of smart card readers in my closet (they’re not even USB, but serial port!) They’re much more popular in Europe, where they’re used in payphones (among other things). Given that wireless NFC seems to be the next ‘big thing’ I really don’t see they’re future use in credit cards as catching on. ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [March 26, 2015, 2:13am UTC](https://boards.straightdope.com/t/the-contact-pattern-on-a-chipped-credit-card/715862/11 "2015-03-26T02:13:45Z")
> [@Hail\_Ants](#): > > They’re much more popular in Europe, where they’re used in payphones (among other things). Given that wireless NFC seems to be the next ‘big thing’ I really don’t see they’re future use in credit cards as catching on. Also in Canada, where AFAIK every credit and debit card is chip-equipped and has been for years, and in fact for security reasons mag stripe use is usually disallowed on POS systems that support the chip, which is virtually all of them. Virtually all credit cards here also support contactless NFC payment systems, too, but these are only allowed for small transactions (amounts vary by merchant) and for a limited number of transactions before use of the chip and PIN is required for validation. That’s because NFC has far less security than the smart chip and unless that fundamentally changes it will not replace the chip but only be a convenient alternative for small payments. Tap-and-go is really quick and convenient, but it’s not a substitute for chip-based validation. ---
**Author:** ![Hail\_Ants](https://avatars.discourse-cdn.com/v4/letter/h/dc4da7/32.png) [@Hail\_Ants](https://boards.straightdope.com/u/Hail_Ants)\ **Post date:** [March 26, 2015, 2:35am UTC](https://boards.straightdope.com/t/the-contact-pattern-on-a-chipped-credit-card/715862/12 "2015-03-26T02:35:35Z")
> [@wolfpup](#): > > Also in Canada, where AFAIK every credit and debit card is chip-equipped and has been for years, and in fact for security reasons mag stripe use is usually disallowed on POS systems that support the chip, which is virtually all of them. > > Virtually all credit cards here also support contactless NFC payment systems, too, but these are only allowed for small transactions (amounts vary by merchant) and for a limited number of transactions before use of the chip and PIN is required for validation. That’s because NFC has far less security than the smart chip and unless that fundamentally changes it will not replace the chip but only be a convenient alternative for small payments. Tap-and-go is really quick and convenient, but it’s not a substitute for chip-based validation. What’s weird is that I have seen dual mag-strip/smart chip credit card readers here in the US, but I have never, ever, not even once seen one used with a credit card’s smart card chip. Everyone still just swipes… ---
**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\ **Post date:** [March 26, 2015, 3:36am UTC](https://boards.straightdope.com/t/the-contact-pattern-on-a-chipped-credit-card/715862/13 "2015-03-26T03:36:21Z")
I just visited Singapore and everywhere I just signed. Dunno if this is because they expect visitors cards to not work? (Visa, MC, American Express). They all had normal swipe + C&P readers, but did not use them for my purchases. ---
**Author:** ![MarcusF](https://avatars.discourse-cdn.com/v4/letter/m/67e7ee/32.png) [@MarcusF](https://boards.straightdope.com/u/MarcusF)\ **Post date:** [March 26, 2015, 7:36am UTC](https://boards.straightdope.com/t/the-contact-pattern-on-a-chipped-credit-card/715862/14 "2015-03-26T07:36:36Z")
> [@Hail\_Ants](#): > > What’s weird is that I have seen dual mag-strip/smart chip credit card readers here in the US, but I have never, ever, not even once seen one used with a credit card’s smart card chip. Everyone still just swipes… In the UK Chip & Pin is universal but the magnetic strips are still active. The supermarket “scan as you shop” systems require you to swipe your card to release the hand held bar-code reader and then to download the data before using the chip & pin on the same card and card reader to pay. Back on the OP, it’s an interesting question. A quick check of the four (!) cards in my pocket show three different patterns (the two the same are a debit and credit card from the same bank) but the central core of seven - three on each side and a big one between them- look to be the same on all of them. The newer cards have contactless payment built in but in the UK this is limited to 20 pounds per transaction (this will go up to 30 later this year) so it is not going to drive out chip & pin any time soon. ---
**Author:** ![Hail\_Ants](https://avatars.discourse-cdn.com/v4/letter/h/dc4da7/32.png) [@Hail\_Ants](https://boards.straightdope.com/u/Hail_Ants)\ **Post date:** [March 26, 2015, 7:12pm UTC](https://boards.straightdope.com/t/the-contact-pattern-on-a-chipped-credit-card/715862/15 "2015-03-26T19:12:53Z")
> [@MarcusF](#): > > In the UK Chip & Pin is universal but the magnetic strips are still active. The supermarket “scan as you shop” systems require you to swipe your card to release the hand held bar-code reader and then to download the data before using the chip & pin on the same card and card reader to pay. The semi-national supermarket chain I frequent (Stop & Shop) uses [a scan as you shop system](http://stopandshop.com/shopping/shopping-tools/scanit/). It’s the only place I’ve ever seen one. Here there’s just an optical bar code scanner that scans your courtesy card to release the scanner. After that you just pay however you want, with cash or credit/debit. They do allow you to ‘link’ your courtesy & credit card to automatically pay at the end but I don’t like the idea of that. ---
**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\ **Post date:** [May 6, 2015, 5:47am UTC](https://boards.straightdope.com/t/the-contact-pattern-on-a-chipped-credit-card/715862/16 "2015-05-06T05:47:37Z")
> [@Hail\_Ants](#): > > What’s weird is that I have seen dual mag-strip/smart chip credit card readers here in the US, but I have never, ever, not even once seen one used with a credit card’s smart card chip. Everyone still just swipes… I just recalled – in AUS the card readers were in the supermarkets 10 years before they came into use. Somewhere in the 90’s, soon after mobile phones became common. That whole generation of smart-card readers / swipe readers was worn out and discarded before it ever saw a smart-card used for payment.